Solar Eruptions are Not Slinky in Shape

September 9, 2018

A recent study raises some considerable questions about the shape of solar eruptions.

Elizabeth A. Jensen, a PSI Associate Research Scientist and her team used the Green Bank Observatory in West Virginia to observe radio signals from the MESSENGER spacecraft. They discovered secondary trailing impacts that accompany solar eruptions that cause communication disruptions and electrical grid failures when they impact Earth. These coronal mass ejections (CMEs), often associated with solar flares, are powerful and can trigger geomagnetic storms. Jensen spoke about them and said,

“The most powerful CMEs may travel at 2,000 kilometers per second, passing the Earth in seconds. We have discovered reconnection regions trailing behind a CME traveling 750 kilometers per second. This suggests that the impact of a CME on the Earth’s space weather consists of the initial shock from the CME and also secondary shocks from powerful electrical currents and accelerated plasmas trailing in the CME’s wake. These secondary regions trailing the CME front have never been seen before because we have had few opportunities to probe this area with spacecraft. The MESSENGER spacecraft orbiting Mercury on the other side of the Sun was in the right place at the right time to observe a CME safely by passing radio signals through it to the Earth. Understanding the three-dimensional structure of these eruptions that strike the Earth is essential to properly preparing for their potential effects.”

CMEs affect human activity and technology in space, within the atmosphere and reach the ground. In 1989, a powerful CME disrupted satellites orbiting Earth along with the space shuttle Discovery, and electric grids, causing a blackout in Canada. On August 31, 2012, a long filament of solar material that had been hovering in the sun’s atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The coronal mass ejection, or CME, traveled at over 900 miles per second. The CME did not travel directly toward Earth but did connect with Earth’s magnetic environment, or magnetosphere, causing aurora to appear on the 3rd of September.

It is said, “Everything old is new again.” While the phrase commonly refers to fashion, design, or technology, scientists at the University of New Hampshire found the truth to this saying in research as well. Having revisited older data, researchers discovered new information about the shape of CMEs, large-scale eruptions of plasma and magnetic field from the sun, which could help protect satellites in space as well as the electrical grid on Earth. Noe Lugaz, a Research Associate Professor in the UNH Space Science Centre, mentioned that in the following words:

“Since the late 1970s, coronal mass ejections have been assumed to resemble a large Slinky – one of those spring toys—with both ends anchored at the sun, even when they reach Earth about one to three days after they erupt. But our research suggests their shapes are possibly different.”

According to the study published in the ‘Astrophysical Journal Letters’, the researchers revisited the data from ‘Wind and ACE’, two NASA spacecraft charged with orbiting upstream of Earth. They analyzed 21 CMEs collected between 2000 and 2002 when Wind had separated from ACE by 1% of one astronomical unit (AU). The Wind was perpendicular to the Sun-Earth line instead of being in front of Earth, with the ACE. Lugaz explained that by saying,

“Because they are usually so close to one another, very few people compare the data from both Wind and ACE. But 15 years ago, they were apart and in the right place for us to go back and notice the difference in measurements, and the differences became larger with increasing separations, making us question the Slinky shape.”

This analysis offered other shape possibilities for the CMEs. They could either be Slinky-shaped but roughly four times smaller than previously thought, or they might be deformed ones. Similarly, it is quite possible that they are something entirely different.

Even though CMEs create beautiful and intense auroras (Northern and Southern Lights), they damage satellites, disrupt radio communications, and wreak havoc on the electrical transmission system causing massive and long-lasting power outages. Thus, knowing the shape and size of CMEs is important to accurately forecast when and how they will impact the Earth. Currently, only single point measurements exist making CME shape detection difficult. However, recent findings have allowed space forecasters to issue warnings 30 to 60 minute before impact. Their ultimate aim is to have a notice time of 24 hours so that informed decisions could be made.

For this reason, researchers believe that more research is needed. Lugaz thinks this information is potentially important for future space weather forecasting as NASA and NOAA are considering future missions. Scientists acknowledge that this study does highlight the need for future spacecraft to first investigate how close to the Sun-Earth line they must remain for more advanced forecast predictions.

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